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The MicroBlaze ABI has the caller reserve stack space for the arguments
it passes in registers: REG_PARM_STACK_SPACE is 24 and
OUTGOING_REG_PARM_STACK_SPACE is 1 in the gcc backend, so a callee may
write to [caller_sp + 4, caller_sp + 28). The kernel calls C functions
from entry.S with r1 pointing at pt_regs, handing the callee license to
spill its incoming arguments over the saved registers -- the syscall
dispatch is the worst case, where the first argument slot is PT_R1, the
saved user stack pointer.
This was latent until GCC 15: since 3b9b8d6cfdf5 ("ira: Scale
save/restore costs of callee save registers with block frequency") the
allocator prefers spilling incoming arguments over copying them into
callee-saved registers, and a kernel built with gcc >= 15 (without the
TARGET_CALLEE_SAVE_COST workaround some distributions carry) corrupts
PT_R1 on the first syscall: init takes SIGSEGV and the kernel panics.
The kernel had exactly this reservation until 2011:
commit 6e83557c38b4 ("microblaze: Remove r0_ram pointer and PTO alignment")
removed STATE_SAVE_ARG_SPACE and with it the PTO offset, as part of
cleaning up what was thought to be copied-from-v850 leftovers. Restore
it: the frame is STATE_SAVE_SIZE = PT_SIZE + PTO, r1 stays at the frame
base through every asm-to-C call, and the saved registers are reached
at r1 + PTO + PT_*. PTO is 28 rather than the historic 24, which was
one word short: FIRST_PARM_OFFSET is 4 and REG_PARM_STACK_SPACE is 24,
so the area spans [sp+4, sp+28) and needs 28 bytes. With 24 the last
argument slot overlapped pt_regs' r0 -- harmless only because r0 is the
constant-zero register. STACK_BOUNDARY is 32 bits, so 28 needs no
further rounding.
Two places deliberately keep their mainline addressing.
hw_exception_handler.S needs no offset change: its real-mode handler
saves into the standalone pt_pool_space buffer rather than a stack
frame, and _unaligned_data_exception works through a pointer to pt_regs
in r7, where plain PT_* offsets are already right. And the user-SP
reload after popping the frame keeps PT_R1 - PT_SIZE because PTO
cancels there: (PTO + PT_R1) - (PT_SIZE + PTO) = PT_R1 - PT_SIZE. Both
are exactly as the pre-2011 code had them.
The instruction count is unchanged -- the same instructions with
different immediates, no per-call reservation and no trampolines. The
cost is 28 bytes more kernel stack per saved frame.
Fixes: 6e83557c38b4 ("microblaze: Remove r0_ram pointer and PTO alignment")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5
Signed-off-by: Ramin Moussavi <ramin.moussavi@yacoub.de>
Tested-by: Waldemar Brodkorb <wbx@openadk.org>
Link: https://patch.msgid.link/20260821151809.1233057-5-ramin.moussavi@yacoub.de
Signed-off-by: Michal Simek <michal.simek@amd.com>
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While the GCC and Clang compilers already define __ASSEMBLER__
automatically when compiling assembly code, __ASSEMBLY__ is a
macro that only gets defined by the Makefiles in the kernel.
This can be very confusing when switching between userspace
and kernelspace coding, or when dealing with uapi headers that
rather should use __ASSEMBLER__ instead. So let's standardize on
the __ASSEMBLER__ macro that is provided by the compilers now.
This is a completely mechanical patch (done with a simple "sed -i"
statement).
Cc: Michal Simek <monstr@monstr.eu>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Link: https://lore.kernel.org/r/20250314071013.1575167-19-thuth@redhat.com
Signed-off-by: Michal Simek <michal.simek@amd.com>
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Covert all headers to SPDX.
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Stefan Asserhall <stefan.asserhall@xilinx.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
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compiling issue
"entry.h" needs 'asmlinkage', and "asm/linkage.h" does not provide it.
So need include "linux/linkage.h" to use generic one instead of.
The related error (with allmodconfig under microblaze):
CC [M] drivers/net/ethernet/emulex/benet/be_main.o
In file included from ./arch/microblaze/include/asm/processor.h:17:0,
from include/linux/prefetch.h:14,
from drivers/net/ethernet/emulex/benet/be_main.c:18:
./arch/microblaze/include/asm/entry.h:33:19: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void'
extern asmlinkage void do_notify_resume(struct pt_regs *regs, int in_syscall);
^
Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
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Fix sparse warning by declaration do_notify_resume function
called from entry.S.
Warning:
arch/microblaze/kernel/signal.c:357:6: warning: symbol
'do_notify_resume' was not declared. Should it be static?
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
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r0_ram pool was used for saving/restoring register
content if hw exception happen. This poll was replaced by
pt_pool_space with PT_SIZE size.
Based on this change SAVE_STATE_ARG_SPACE was removed which
caused that PTO offset is zero that's why is also removed.
r0_ram space was used as scratchpad by v850. In early
Microblaze Linux developing phase was this part of code
blindly copied.
Signed-off-by: Michal Simek <monstr@monstr.eu>
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Now that the return from alloc_percpu is compatible with the address
of per-cpu vars, it makes sense to hand around the address of per-cpu
variables. To make this sane, we remove the per_cpu__ prefix we used
created to stop people accidentally using these vars directly.
Now we have sparse, we can use that (next patch).
tj: * Updated to convert stuff which were missed by or added after the
original patch.
* Kill per_cpu_var() macro.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
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Signed-off-by: Michal Simek <monstr@monstr.eu>
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For noMMU kernel this change nothing bring but this change
helps with MMU synchronization.
Signed-off-by: Michal Simek <monstr@monstr.eu>
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Signed-off-by: Michal Simek <monstr@monstr.eu>
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Reviewed-by: Ingo Molnar <mingo@elte.hu>
Acked-by: John Linn <john.linn@xilinx.com>
Acked-by: Stephen Neuendorffer <stephen.neuendorffer@xilinx.com>
Acked-by: John Williams <john.williams@petalogix.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>
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